1. Field of the Invention
The present invention relates to a writing instrument, and more particularly, to a writing instrument including an ink tank, an ink intake retainer body, a tubular drawing tip, and an ink drain restriction body for absorbing volume expansion caused by variation in temperature of ink, which is absorbed in the ink intake retainer body, wherein the ink drain restriction body is disposed on the part of an air passage of the ink intake retainer body, whereby the ink is prevented from flowing toward the air passage by means of its weight when the writing instrument is carried upside down.
2. Background of the Related Art
Generally, a writing instrument includes an ink tank for containing ink, and a tubular drawing tip for drawing the ink contained in the ink tank by way of a capillary phenomenon for writing purpose.
Meanwhile, as described above, if the ink is directly supplied from the ink tank to the tubular drawing tip, it becomes difficult to control the outflow of the ink through the tubular drawing tip. In this connection, in order to prevent excessive outflow of the ink, an ink intake retainer body for temporarily storing the ink supplied from the ink tank is disposed between the tubular drawing tip and the ink tank.
An air passage for enabling the ink to flow smoothly is further formed in the rear of the ink intake retainer body on the part of the tubular drawing tip body.
In the writing instrument constructed above, the ink contained in the ink retainer tank is absorbed/stored by/in the ink intake retainer body, and then flows toward the tubular drawing tip, so that writing is accomplished.
However, as stated previously, if ambient temperature varies while using such a conventional writing instrument having a mixing ball provided in the ink retainer tank, the ink, which is absorbed/stored by/in the ink intake retainer body, flows toward the air passage by means of volume expansion. In this case, however, there are problems in that the flowed ink stops the air passage and flows outside the body because of wetting by viscosity with the surface of the body.
Furthermore, if the writing instrument is held upside down or applied with shock from the back, the ink stored in the ink intake retainer body flows toward the air passage by way of inertia flow. Accordingly, there are problems in that the flowed ink plugs the air passage and flows outside the body because of wetting by viscosity with the surface of the body.